This invention relates to tube support sheets and more particularly to support sheets for closely packed tubes. Nuclear steam generators have had problems with the buildup of deposits between the tubes and the tube support sheets wherein the holes in the tube support sheets through which the tubes pass are only slightly larger in diameter than the tubes allowing the buildup of deposits therebetween resulting in a sphincter crushing of the tubes at the tube sheet. The close proximity of the tube sheet to the tube impairs the flow of fluid along the tube and results in poor heat transfer between the tube and the fluid flowing along the outer side of the tube adjacent the tube sheet.